A wooden chair is known from U.S. Pat. No. 1,744,799 with a frame which consists of a crossrib screwed to a seat, four chair legs screwed to the two planar rib parts of the crossrib, and a crossbar construction which reinforces the chair frame; the two planar bars of the crossbar construction are screwed to the bottom sections of the chair legs. Both the two rib pans and the two bars are weakened by cutouts in the junction with a depth which corresponds to half the rib or bar height. Due to the inadequate flexural and torsional strength of the crossrib the seat is made correspondingly strong and thus very hard so that it is not possible to sit comfortably in the chair, as would be desirable. To increase the strength of the crossrib construction a reinforcing plate with bent projections which surround the bars is attached to the top of the two bars at the junction.
When the long rib parts for the crossrib and the long bars for the crossbar construction of this known chair are cut out from boards, due to knots, knotholes, etc. comparatively large amounts of waste material are formed, so that due to the required amount of wood for the crossribs and crossbars the chair becomes too expensive for mass production.
The same disadvantage applies to commercially available seating furniture and tables of wood with crossribs which consist of one long rib part and two short rib parts which are dowelled to the long rib part.
Because of this construction, the known crossribs, due to the vertical and horizontal forces which occur, are subject to flexural and torsional stresses which can cause the wood connecting elements, especially dowels, to break. Finally, chair and table frames with crossribs with rib parts which exceed a certain length tend to instability.
A rib frame for stacking chairs and armchairs with a front and a rear rib as well as two side ribs of wood is known from DE 37 08 991 C1. The front rib of the rib frame is connected by its two ends via tenons to the two front chair legs and is mortised in the end regions to the side ribs. The rear rib consists of two subribs located in a V-shape in one horizontal plane; their ends pointing outwards are mortised to the two rear chair legs. In addition, the two subribs in their outer section are each mortised to a side rib and the inside ends of the subribs which taper to a point are mortised obliquely to a middle bar which connects the side ribs in the center of the bar.
This complex rib construction is comparatively expensive due to the amount of wood needed to produce it.
The problem of the invention is to develop a structurally simple, stable, and cost favorable crossrib of wood for seating furniture and tables.